1. Field of the Invention
The present invention relates to a phacoemulsification handpiece and, more particularly, to a handpiece which provides fingertip control of ultrasonic energy during a phacoemulsification procedure.
2. Description of the Related Art
The human eye is divided by a normally transparent lens into anterior and posterior chambers. The transparent lens focuses light onto the retina defined on the rear surface of the posterior chamber. The lens of the eye may become cloudy for any one of a variety of reasons. When this happens, sight is impaired and the cloudy lens material must be removed. The function of the lens is then performed with an intraocular lens (IOL) implant or by using thick glasses or contact lenses.
A number of techniques are now being used for removing the cloudy, cataractous lens material. In all these techniques, a surgical tool is inserted into the eye through an incision. The phacoemulsification technique is a recently developed technique which is being used with increasing frequency. With that technique, an incision is made in the eye and a probe is inserted into the eye and into contact with the cataract tissue. Irrigation and aspiration passages are each defined through the probe and the probe is operatively coupled to a source of ultrasonic energy. Ultrasonic energy is selectively applied to the probe to break up the cataract tissue in contact with the tip of the probe so that the cataract tissue can be aspirated together with irrigating liquid. More particularly, the probe is manipulated to engage the harder cataract tissue which is then held in place by the aspiration and phacoemulsified by moving a foot pedal to activate ultrasound energy. The intensity of the ultrasound energy which can be applied is typically preselected by the surgeon. Ultrasonic energy is delivered as long as the foot pedal is held in position and is sufficient for phacoemulsifying the particles of cataract material.
Some conventional foot switches utilized with phacoemulsification machines and handpieces have four positions. There is a completely off position, where the foot pedal is not depressed at all, and an irrigation position, actuated by partial depression of the foot pedal. A combination of irrigation and aspiration is effected by a further depression of the foot pedal. Finally, there is an irrigation, aspiration and phaco position. With such a system, a fixed aspiration level is provided and the application of ultrasonic energy is either linear, that is a certain percent of power depending upon the disposition of the foot pedal, or fixed, that is a certain percent of power which is preselected by the surgeon.
In other conventional systems, a foot pedal is provided wherein there is a zero, or everything off, position, a first position where an irrigation fluid is supplied to the surgical site and a second position for irrigation and aspiration. With that system, instead of a fixed aspiration level, aspiration is linear from zero to the maximum millimeters of mercury which can be applied through the particular handpiece. Main phaco switching is provided to the right of the aspiration/irrigation foot pedal and is actuated by moving the foot to the right.
A disadvantage of the foregoing conventional systems is that the foot is utilized to control all the functions of the handpiece, specifically irrigation, aspiration and phaco whether linear or fixed. Because the foot does not have the touch sensitivity or fast, controlled response possible with, for example, the human hand, particularly when shoes are worn, it is difficult for the surgeon using his foot to properly time the application of phaco as well as to sense the amount of phaco being provided, when a linear application of phaco is utilized. Therefore, it would be desirable to provide a system for controlling ultrasonic energy delivered to a phacoemulsification handpiece which does not require use the surgeon's foot and hence does not exhibit the inherent inaccuracy and lack of control of conventional systems.